1. Field of the Invention
The present invention relates to an ultrasonic diagnosis apparatus suitable for diagnostical imaging and quantitative analysis for medical purpose.
2. Description of Related Background Art
Electronic focussing type ultrasonic diagnosis apparatus are widely used for diagnosing various parts of human body such as an abdomen, because it has an adequate imaging range covering from a near field to a far field. An example of ultrasonic diagnosis apparatus is shown in U.S. Pat. No. 4,759,372 and others. In a paper by the inventors of this invention appearing in Japanese Journal of Medical Ultrasonics, vol. 14, Supplement I, 1987, at pp. 317 to 318, discussed for a curved array transducer probe combined with impedance matching layers and an acoustic lens for narrowing a beam width in the direction perpendicular to the beam scanning direction, is beam refraction at the interlayers in the beam scanning direction influencing the focussing.
There is also described in U.S. Pat. No. 4,566,459 that an electronic focussing error occurs in a linear array transducer probe depending upon a sound speed of organ tissue to be diagnosed, and the technique of measuring an average sound speed within organs by positively using such phenomenon.